3 ms·

What is a definition of a "feature" in this instance? Does it just mean the current state of a system that could be modeled as a single phase-space (i.e. locati

by fsloth 11y ago

What is a definition of a "feature" in this instance? Does it just mean the current state of a system that could be modeled as a single phase-space (i.e. location plus momentum space for the non-physicists)?

fsloth 11y ago
No, really, I have MSc in physics but I have no idea what a thing being 'a feature' specifically means in the cosmological sense - quick googling also fails to find specification for the term. If it's significant then it is significant within a specific model and elements of said model should be able to be specified with logical precision - otherwise the said model is kinda pointless. Clearly what they are seeing is a large scale anisotropy - so what's the treshold for an anisotropy to be considered to be 'a single structure' and how is it measured?
eevilspock 11y ago
It's implied by his equating "feature" to "structure" and his references to a "Cosmological Principle" that "indicate that the structure of the cosmos is uniform on the largest scales" and that "this new discovery challenge the principle, which sets a theoretical limit of 1.2 billion light years for the largest structures." Think of it in terms of the Second Law of thermodynamics. Local increases in order (decreases in entropy), such as there formation of stars or the emergence and spread of life, apparently violate the law, but in fact do not when you look at a greater scope. Order is decreases at "the largest scales". So by "feature" and "structure" he means a local violation of this principle of uniformity. Apparently this arrangement of GRB's cannot be random non-uniformity, thus implying it is some kind of structure. For example if you flip a coin a million times you will get some clumsiness, periods with far more heads or far more tails. But if clumpy periods exceed a certain size, you would start to suspect that the coin is biased or rigged. It would be violating your expectations given truly random coin tosses. Or as skwosh said in another comment, "It's considered a feature I think not just because it's a ring but because it's an area of higher than expected density of Gamma Ray Bursts (GRBs)."

by fsloth 11y ago

fsloth 11y ago

No, really, I have MSc in physics but I have no idea what a thing being 'a feature' specifically means in the cosmological sense - quick googling also fails to find specification for the term. If it's significant then it is significant within a specific model and elements of said model should be able to be specified with logical precision - otherwise the said model is kinda pointless. Clearly what they are seeing is a large scale anisotropy - so what's the treshold for an anisotropy to be considered to be 'a single structure' and how is it measured?

eevilspock 11y ago

It's implied by his equating "feature" to "structure" and his references to a "Cosmological Principle" that "indicate that the structure of the cosmos is uniform on the largest scales" and that "this new discovery challenge the principle, which sets a theoretical limit of 1.2 billion light years for the largest structures." Think of it in terms of the Second Law of thermodynamics. Local increases in order (decreases in entropy), such as there formation of stars or the emergence and spread of life, apparently violate the law, but in fact do not when you look at a greater scope. Order is decreases at "the largest scales". So by "feature" and "structure" he means a local violation of this principle of uniformity. Apparently this arrangement of GRB's cannot be random non-uniformity, thus implying it is some kind of structure. For example if you flip a coin a million times you will get some clumsiness, periods with far more heads or far more tails. But if clumpy periods exceed a certain size, you would start to suspect that the coin is biased or rigged. It would be violating your expectations given truly random coin tosses. Or as skwosh said in another comment, "It's considered a feature I think not just because it's a ring but because it's an area of higher than expected density of Gamma Ray Bursts (GRBs)."